cinder volume service keeps retrying even code exception

Make sure that ProcessLauncher does not try to restart the failed
service. And make sure the ProcessLauncher exits, when the number
of the failed services equal the number of total services.

Fixes: bug 1167841
Change-Id: I818c754534c18a62d292e21f0c98086571fe0565
(cherry picked from commit 2cee8fc3a4899097801ad93b5d6e6a4f373ad8fe)
Merge "cinder volume service keeps retrying even code exception" into stable/grizzly